The present invention relates to an image recording apparatus employing a fixing unit having a pair of fixing rollers.
Conventionally, an image recording device is known which utilizes an electrophotographic system in which a surface of a photoconductive drum is exposed to light to form a latent image on the drum surface. Toner is then applied to the latent image to develop the image, and the developed image is transferred onto a recording sheet and is fixed at a fixing station. Such an image recording device is chiefly employed in copying machine. In recent years, however, the image recording device has been utilized in a printer or the like, for printing out output from a computer, one of which is a laser beam printer.
The laser beam printer comprises, for example as illustrated in FIG. 1, a photoconductive drum 1. Arranged about the photoconductive drum 1 in order of the rotational direction thereof are a charging station A, an exposure station B, a developing station C, a transferring station D, a toner-cleaning station E, and a discharge station F.
The arrangement is such that at the exposure station B, the laser beam scans the surface of the drum 1 which has been uniformly charged at the charging station A, to thereby form a latent image on the charged drum surface. Toner is then applied at the developing station C to the latent image to develop the same. Subsequently, the developed toner image is transferred at the transferring station O onto the recording sheet P which is fed at a velocity identical with the circumferential speed of the photoconductive drum 1.
The recording sheet P carrying the toner image transferred thereon at the transferring station D is guided and/or fed by guide rollers to a fixing station G. The recording sheet P is then heated and/or pressed at the fixing station G in order for the toner image to be fixed onto the surface of the recording sheet P.
As for the fixing station G, various types have hereto fore been known in this field and a fixing station of the heat roller type capable of high-speed operation with high thermal efficiency is generally used
The heat roller type comprises a heat roller whose surface is heated by a heat source such as a halogen lamp up to approximately 160.degree. C.-200.degree. C. and a press roller (backup roller) coated with heat resistant elastic material. Both rollers are disposed face to face. While the press roller is used to press the heat roller under predetermined pressure a, recording sheet carrying an unfixed toner image is passed therethrough, whereby the toner image is fixed onto the recording sheet as the toner is fused by the heat applied from the heat roller.
However, the disadvantage of the conventional fixing station is that, since the heat and press rollers are forced to abut each other under the predetermined pressure, the recording sheet cannot readily be removed during maintenance interruption while the recording sheet is fed to the fixing station, i.e. in between both the rollers.